Actuator Bonding Optimization and System Control of a Rotor Blade Ultrasonic Deicing System

Abstract

The use of ultrasonic excitation has shown the ability to promote ice shedding of impact ice (<2 mm thick) during prior wind tunnel testing efforts. The ultrasonic deicing technology is implemented to structures representative of rotorcraft blade leading edges and tested under impact icing and centrifugal environments (390 gs). Finite Element Models (FEM) are experimentally validated and used to predict the ultrasonic ice shedding transverse shear stresses responsible for ice shedding. The FEM tools are then utilized to guide the design of an optimized bondline between the PZT actuators and the host structure forming the ultrasonic deicing system. The novel bondline approach is implemented to a rotor blade leading edge erosion cap representative structure (0.813 mm thick stainless steel leading edge). The system is tested under centrifugal loads and icing conditions generic to helicopter operational envelopes. Details on the optimized system fabrication and integration are provided. The optimized bondline configuration does not degrade during operation and increases the ice interface transverse shear stresses by 15% with respect to prior bonding approaches. To promote ice shedding of impact ice, a system control to identify and excite optimum deicing modes during rotor ice testing is also implemented and described in this paper. The power consumption of the deicing system is quantified to average 0.63 W/cm 2 . The deicing system is able to promote shedding of ice layers ranging from 1.4 to 7.1 mm in thickness for varying icing conditions within FAR Part 25/29 Appendix: C Icing Envelope.

Electromechanical Resonant Ice Protection Systems: Analysis of Fracture Propagation Mechanisms

“…In order to develop models for the design and analysis of piezoelectric systems, it is interesting to determine the main physical effects involved in de-icing. Many authors have set up video recordings [12][14] [22] during their tests. The speed of the fracture phenomena, with time constants lower than milliseconds, is emphasized by the use of fast video cameras.…”

“…The two phenomena can be consecutive without interruption or can require an increase in voltage magnitude or change of frequency to occur after a first fracture. In the tests reported in the literature, the activation of the support is generally carried out by a sweep over the frequency ranges that can excite extensional [6].. [12] or flexural [13].. [15][22] modes. For all of these modes, it is possible to note a change in the resonance frequency with the thickness of the ice and a significant amplification of the vibrations at resonance.…”

Ultrasonic Ice Protection Systems: Analytical and Numerical Models for Architecture Tradeoff

“…Palacios initiated many studies on de-icing systems [16] [21] and tested several technologies. For piezoelectric de-icing systems, he used piezoelectric patches to generate ultrasonic shear stress at high frequency (around a few tens of kHz).…”

“…In [20], experiments showed two main failures related to the bonding of the actuators: fracture of the piezoelectric ceramic at the solder joint location and delamination between the ceramic and the host. To tackle this problem, Palacios proposed optimizing the bonding of the supply wire on the ceramic and the bonding between the piezoelectric actuators and the substrate to avoid concentrations of stresses [21]. In [22], he also investigated the effect of hydrophobic coating combined with an ultrasonic deicing system and showed that the ice adhesion depended on the substrate roughness.…”

Analysis of Piezoelectric Ice Protection Systems Combined with Ice-Phobic Coatings

“…It has the disadvantage of a risk of mechanical failure for too high vibration levels. Palacios noted this type of failure in his publications and reports 12,13 . Table 3 shows the evolution of the characteristic quantities (frequency, voltage and power) leading to deicing for a beginning of delamination in one point and for a delamination over 55% of the surface.…”